In studying the woolly mammoth fossil collections of several European museums, researchers have determined that the giant tusked mammal of prehistoric times more frequently developed cervical ribs than do modern elephants and similar species.

A cervical rib, which is a rib attached to a cervical vertebra, or neck, is not itself a life-threatening condition. But its presence is relatively unusual, and treated by experts as a signal that something else is awry -- specifically, that some other genetic or environmental problems were present during embryonic development. That's why biologists usually associate cervical ribs with still births and genetic abnormalities.

As such, researchers at the Rotterdam Museum of Natural History and the Naturalis Biodiversity Center in Leiden believe the increased incidence of cervical ribs in ancient mammoths may explain their hastened decline 10,000 years ago.

The Dutch paleontologists began investigating other European mammoth collections after several newly discovered vertebras -- unearthed along the coast of the North Sea -- showed signs of having had ribs attached where they normally aren't.

After studying other North Sea specimens, scientists found that the same rib abnormality was present in 33 percent of ancient mammoths.

"It had aroused our curiosity to find two cervical vertebrae, with large articulation facets for ribs, in the mammoth samples recently dredged from the North Sea," explained Jelle Reumer, one of the authors of the new study. "We knew these were just about the last mammoths living there, so we suspected something was happening. Our work now shows that there was indeed a problem in this population."

The researchers say that given the birth defects associated with this abnormality, it is likely that the increased presence of neck ribs played a role in the mammal's eventual extinction.

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